1. Field of the Invention
The present invention relates to an image processing method for correcting a red eye phenomenon occurring in photographically recorded image data and relates also to an apparatus for implementing this method.
2. Description of the Related Art
In flash pictures of such subject as a human or an animal, there can occur a so-called red eye phenomenon resulting from reflection of the flash light off the blood vessels of the retina of the subject's eyes, causing the center of the pupils of the eyes to appear red or in a color different from the actual color thereof. With ever increasing popularity of digital cameras as well as film scanners for digitizing photographic image of a photographic film, various and numerous solutions have been proposed to tackle this problem by means of image processing technique. Of course, correction of red eye phenomenon is possible by a professional technique in which a skilled artisan manually corrects the color of each of pixels of the red eye to its correct color while observing these pixels on a monitor. However, this technique is unpopular since this is extremely troublesome and requires high skill on the part of the artisan. For this reason, there has been proposed an automatic method in which the pupil in the picture is detected by using e.g. a pattern recognition technique or a red portion is picked out from within the image and color change is made on this detected portion. In this case, however, for precise detection of red eye area, very complicated image processing technique is required and also the system implementing the technique tends to be very expensive.
According to another solution known from Japanese Patent Application “Kokai” No. 2000-76427 (paragraphs [0009] to [0011] and [0058] to [0071], and FIG. 10), a read eye portion is separated from a white eye portion and a skin color portion. In this, first, an area including the eye area having the color defect is designated. Then, for this designated area, the technique uses characteristics amounts comprising combination of e.g. brightness and reddishness and utilizes a fact that a trough is formed respectively between the red eye portion and the white eye portion and between the red eye portion and the skin color portion, so that the area is divided for each high point in the characteristics amount. In the red eye portion, the closer to the center of pupil, the stronger the reflection from the retina. So that, the brightness tends to decrease from the center to the peripheral portion, resulting in hill-like distribution of the brightness, including “catch light” in the eye. Also, in the case of an eye having bluish iris, there is formed a trough between a red eye portion and the iris in the magnitude of the redness. The above conventional technique utilizes these phenomena. That is to say, this technique is configured to achieve the separation of the red eye portion from the white eye portion and the skin color portion, based on the intensity distribution of color-related attribute, i.e. the redness, in the eye area, rather than discriminate red eye pixels through detections of red, white, skin color pixels. Moreover, as this conventional technique requires designation of the eye area in advance, for realizing its full automization, a new technology will be needed for image recognition of the eye area, which technology is difficult to achieve.
A still further solution is proposed by e.g. Japanese Patent Application “Kokai” No. 6-258732 (paragraphs [0006] to [0009] and [0019] to [0023], and FIG. 6). This solution comprises a technique for detecting a red eye portion in a photographed subject through extraction of a plurality of color component images unique to a face of a human subject. More particularly, from within a photographic image, at least either a low chroma area or low illumination area and a skin color area are extracted. Then, by using extracted signals, e.g. by effecting a logical AND operation thereon, an area including the subject's eye is extracted. Further, by using the extracted red signals, the red eye position is detected from this area including the eye, if a red eye phenomenon is present therein. Then, based on the red eye position data thus obtained, the red color in the red eye position is corrected to a normal color such as black color. This technique does not require the preliminary designation of the eye area. However, as this technique recognizes a red eye portion based on the skin color and the red color, an erroneous recognition tends to occur.